1. Field of the Invention
The disclosed invention relates to semiconductor devices using complementary metal oxide semiconductor (CMOS) circuits.
The semiconductor device in this specification indicates all the devices that can operate by utilizing semiconductor characteristics. For example, such semiconductor devices widely include the following elements: a semiconductor element (including a so-called power device) such as a transistor, a diode and a thyristor, a logic circuit such as an inverter, an integrated circuit such as an image sensor, a memory and a converter, an integrated circuit including the above elements and a display device typified by a liquid crystal display device, and the like.
2. Description of the Related Art
A CMOS circuit is a necessary component for a semiconductor integrated circuit because the CMOS circuit has low power consumption and can operate at high speed and can be highly integrated. However, in recent years, there is a problem of an increase of power consumption in accordance with miniaturization of a MOS transistor. For example, power consumption in a non-operation period is increased because of leakage current of a transistor included in a CMOS circuit.
Patent Document 1 discloses a technique by which a switching transistor is further provided in a CMOS circuit in order to suppress an increase of leakage current.